template class mola::FixedDenseGrid3D

Overview

A dense 3D grid of NxNxN cells with N = 2^SIDE_NUM_BITS.

All cells are allocated contiguously via calloc (zero-initialized), which is faster than new[] for large arrays because the OS can provide zero-filled pages without actually writing them. For this reason, T must be trivially copyable (enforced by static_assert).

Cell storage order is X-major: cells_[cx + cy*N + cz*N*N]. The bit-shift arithmetic in cellByIndex() exploits the power-of-two side length to replace multiplications with shifts.

This is an internal building block for mola::SparseVoxelPointCloud, where it serves as the dense inner grid inside each sparse outer block.

Parameters:

T	Cell type. Must be trivially copyable.
SIDE_NUM_BITS	log₂ of the number of cells per dimension (e.g. 5 → 32³).
inner_coord_t	Integer type for the index coordinates (e.g. uint32_t).

#include <FixedDenseGrid3D.h>

template <typename T, size_t SIDE_NUM_BITS, typename inner_coord_t>
class FixedDenseGrid3D
{
public:
    // fields

    static constexpr static size_t CELLS_PER_DIM = 1<<SIDE_NUM_BITS;
    static constexpr static size_t TOTAL_CELL_COUNT = 1<<(3* SIDE_NUM_BITS);

    // construction

    FixedDenseGrid3D();
    FixedDenseGrid3D(const FixedDenseGrid3D&);
    FixedDenseGrid3D(FixedDenseGrid3D&&);

    // methods

    FixedDenseGrid3D& operator = (const FixedDenseGrid3D&);
    FixedDenseGrid3D& operator = (FixedDenseGrid3D&&);
    T& cellByIndex(const index3d_t<inner_coord_t>& idx);
    const T& cellByIndex(const index3d_t<inner_coord_t>& idx) const;
    const T* cells() const;
    T* cells();
};